OpenMx library function names

Currently the functions named "omx*" consist of (A) uncommon functions that we intend to remain backwards compatible in all future versions of OpenMx, and (B) uncommon functions that may be helpful to advanced OpenMx users but whose interface might change in the future. We would like to keep type (A) functions in the "omx*" category and rename type (B) functions with a new character prefix. We wish to solicit feedback on which functions should remain in the "omx*" category, and get suggestions for the new prefix string for the type (B) functions.

I'm not sure I'm sold on any of these yet, but using umx has the added benefit that the alphabetic sort order for these goes mx, omx, umx. This is actually a nice thing, in case people go scrolling through function lists or documentation sets. It also won't show up if somebody autocompletes from just an o.

I am a tiny bit concerned about using the term 'unstable', since folks are likely to interpret that differently than we mean it here.

To answer your question, if we decide umxBrownie should move into the fixed user API, we can just move it to be omxBrownie, and make a note in the changelog. This is expected behavior since umx functions are not guaranteed to stay the same. I don't see any reason we'd change something from omx to umx, but if we do, we need to copy it and leave the omx function intact (but deprecated), since those are guaranteed to be consistent. If we decide to move something from omxBrownie to mxBrownie, we'd have to keep both around and available for a couple revisions at least, with omxBrownie deprecated.